Cannabidiol May Be Effective Adjunct to Antipsychotic Treatment for Schizophrenia Patients

Patients with schizophrenia who are prescribed cannabidiol (CBD) in addition to antipsychotics may experience lower levels of positive psychotic symptoms compared with those taking antipsychotics alone, according to a report in AJP in Advance. The study also found that use of CBD as an adjunctive therapy for this population may also improve cognitive performance and overall functioning.

“Because CBD acts in a way different from conventional antipsychotic medication, it may represent a new class of treatment for schizophrenia,” wrote Philip McGuire, M.D., of the Institute of Psychiatry, Psychology, and Neuroscience at King's College London and colleagues. “However, its potential clinical utility will require further investigation in larger-scale trials.”

McGuire and colleagues recruited patients with schizophrenia who had previously demonstrated at least a partial response to antipsychotic medication and had been receiving a stable dose of antipsychotic medication for at least four weeks. A total of 88 patients were randomly assigned to take cannabidiol (1000 mg/day; n=43) or placebo (n=45) in addition to their existing antipsychotic medication.

The researchers evaluated patients’ symptoms, general functioning, and cognitive performance, among other measures at baseline and on days 8, 22, and 43. Clinicians also recorded impressions of patient severity, improvement, and general functioning.

After six weeks, patients in the CBD group experienced a greater reduction in positive psychotic symptoms (measured using the Positive and Negative Syndrome Scale) from baseline compared with the placebo group. At the end of treatment, a significantly higher proportion of patients in the CBD group were rated by their clinician as “improved” on the Clinical Global Impression scale compared with those in the placebo group (78.6% and 54.6%, respectively).

Cognitive performance, as measured by the Brief Cognitive Assessment Scale (BACS), was also greater among patients receiving cannabidiol, although it fell short of statistical significance. However, analysis of the individual BACS domains showed that there was a significantly greater improvement in motor speed in the cannabidiol group compared with the placebo group.

CBD was well tolerated, and rates of adverse events were similar between the CBD and placebo groups.

For related information, see the Psychiatric News article “Cannabidiol May Benefit Patients With Early Psychosis, Cannabis Misuse.”

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